None of the biomarkers of ovarian cancer that have been identified to date is sufficiently predictive of ovarian cancer to be useful as a diagnostic or screening test. We hypothesize that an improved multi-marker panel using longitudinal measurements will provide the requisite high sensitivity and specificity for early detection of ovarian cancer needed for useful screening of target populations. We propose to use novel LabMAP technology that allows for simultaneous evaluation of multiple (up to 100) biomarkers in one sample. Our goal is to develop a reliable serum-based longitudinal assay for early detection of ovarian cancer. Our immediate objectives are (i) to further expand our ovarian cancer panel with additional ovarian cancer-relevant biomarkers including circulating antibodies and proteomic peptides and (ii) to validate the resultant assay for application to clinical screening. To accomplish these objectives the following Specific Aims are proposed: 1. Generate a comprehensive multiplex assay for detection of highly relevant ovarian cancer markers. A Multianalyte Immunobead Diagnostic Assay (MIDAS) will be developed for multiplex analysis of most of the known ovarian cancer serological biomarkers including non-IgG proteins and circulating antibodies. 2. Use biomarker panels identified by MIDAS and MALDI-TOF-MS analyses to select a combined multiplatform multimarker panel that distinguishes women with ovarian cancer from healthy women or women with benign pelvic disease (Phase 2 validation study). Serum samples from women with early stage ovarian cancer, women with benign pelvic disease, healthy controls as well as from women with other cancers will be obtained and screened using a MIDAS array as developed under Specific Aim 1 and by the MALDI-TOFMS technique. A combination of markers distinguishing women with early stage ovarian cancer from those without cancer or with benign disease will be selected. The cancer-specificity of this panel will then be assessed and validated. An optimized statistical model for analyzing and combining multimarker panels will be developed. 3. Validate/optimize this multimarker panel in retrospective longitudinal study (Phase 3 validation study). For this Specific Aim, we will utilize serum samples accumulated in a large prospective trial comprising over 200,000 samples, and will extend the method to evaluating the markers longitudinally. 4. Validate this multimarker panel in prospective longitudinal study (Phase 4 validation study). At the conclusion of this study, we expect to develop strategies for the early detection of ovarian cancer that are practical and efficient and can be projected to offer the best opportunity to reduce the mortality from this disease.